The present invention relates to integrated circuit (IC) device assembly and, more particularly, to lead frames for semiconductor packages.
Many current quad-flat no-leads (QFN) packages include more than one row of leads to increase the number of inputs and outputs (I/Os) while maintaining the package size. FIG. 1 is a cross-sectional side view of a conventional QFN package 100 during lead singulation. The QFN package 100 is assembled using a lead frame 102 that has first and second rows of leads 104 and 106 surrounding a die flag 108. The first and second rows of leads 104 and 106, and the die flag 108 are connected to each other by a plurality of connection bars 110. A die 112 is mounted on the die flag 108 and electrically connected to the first and second rows of leads 104 and 106 with bond wires 114. The lead frame 102, die 112, and bond wires are encapsulated with a molding compound 116.
FIG. 2 shows a top plan view of the lead frame 102 of FIG. 1. After encapsulation, a half-cut process is performed by cutting the connection bars 110 with a blade 118 along a plurality of cutting lines 120 in both the X and Y directions to isolate the leads 104 and 106 from each other, and to isolate the second row of leads 106 from the die flag 108. However, as shown in FIG. 1, the half-cut process risks cutting the bond wire 114 near the lead 106. One way to avoid cutting the bond wires 114 is to attach the bond wires 114 using a wire looping profile with a higher landing angle. However, this can weaken the bond on the lead resulting in a potential reliability risk. In addition, as shown in FIG. 2, the half-cut has to be performed in both the X and Y directions, due to the minimum cutting width required for half-cut, the density of the package I/O is limited. Accordingly, it would be advantageous to have an alternative way to assemble a QFN package with multiple rows of leads.